Theoretical and experimental study of the second-order polarizabilities of Schiff''s bases for nonlinear optical applications

A series of twenty-four Schiff's bases was synthesized and nonresonant static molecular second order polarizabilities (β) of these compounds were theoretically calculated and compared with experimental values. The computational method employed obtained: (a) values of polarization versus static electric fields using a semiempirical Hamiltonian; (b) all tensor elements of β by performing polynomial fits of the former data, within the finite-field approach. The experimental values were obtained using a modified electric field induced second harmonic generation (EFISH) experiment with 1,4-dioxane as the solvent. The measured quantities were the projection of β on μ (the permanent dipole moment), relative to MNA (2-methyl-4-nitroaniline). The correlation between the predicted static molecular quantities and their corresponding experimental values was 0.95 (based on a simple least-squares regression forced through the origin). A factor of 8.7 ± 0.3 was determined to be the adjustment parameter for Schiff's bases to account for the solvent and dispersion effects at the fundamental wavelength of 1064 nm.     

N and p doped poly(3,4-ethylenedioxythiophene) electrode materials for symmetric redox supercapacitors

A symmetric redox supercapacitor has been fabricated based on n and p doped Poly(3,4-ethylenedioxythiophene)(PEDOT) coated on stainless steel (SS) electrodes. The characterization and performance of the supercapacitor has been studied by FTIR, Cyclic Voltammetry and AC Impedance spectroscopy. The supercapacitor showed a maximum specific capacitance of 121 F g⁻¹ at a scan rate of 10 mV s⁻¹. The time constant calculated for the supercapacitor through the active–reactive power behavior measurement was 12 milliseconds indicating the suitability of the system for efficient use at low frequency range.     

Reliability Analysis of Torsional MEMS Varactor

This paper discusses reliability issues in torsional MEMS varactor. Self-actuation due to high ac signals is analyzed, and solutions are proposed. The mode of failure at high actuation voltages is analyzed and established through experiments. Issues like stiction due to high voltages and effect of high residual stress are studied experimentally.     

Type, extent and use of colours in ready-to-eat (RTE) foods prepared in the non-industrial sector – a case study from Hyderabad, India

The type and extent of colours added to ready‐to‐eat (RTE) foods prepared in the non‐industrial sector of India was investigated. Of the 545 RTE foods analysed, 90% contained permitted colours, 2% contained a combination of permitted and non‐permitted colours and 8% contained only non‐permitted colours. However in RTE foods with permitted colours, 73% exceeded 100 ppm, as prescribed by the Prevention of Food Adulteration Act of India, and 27% were within the prescribed levels. Among the permitted colours, tartrazine was the most widely used colour followed by sunset yellow. The maximum concentration of colours was detected in sweet meats (18 767 ppm), non‐alcoholic beverages (9450 ppm), miscellaneous foods (6106 ppm) and hard‐boiled sugar confectioneries (3811 ppm). Among the non‐permitted colours found, rhodamine was most commonly used. Some of the foods, such as savouries and miscellaneous foods like sugar coated aniseed and almond milk, are not supposed to contain colours as per the Prevention of Food Adulteration Act, but were found to contain colours.     

X-ray Diffraction Investigation of the Formation of Nanostructured Metastable Phases During Short-Duration Mechanical Alloying of Cu-Al Powder Mixtures

Mechanical alloying is a powder processing technique used to process materials farther from equilibrium state. This technique is mainly used to process difficult to alloy materials in which the solid solubility is limited, and to process materials where non-equilibrium phases cannot be produced at room temperature through conventional processing techniques. In the present work, mechanical alloying/milling of selected compositions in the Al-Cu binary alloy system was carried out at a ball-to-powder weight ratio (BPR) of 2 : 1, to investigate alloying and subsequent heat treatment on microstructural changes as a result of short milling times. Copper-aluminum powder mixtures containing 5, 20, and 40 wt% Al (11, 37, and 61 at% Al, respectively) were subjected to mechanical alloying, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC), after mechanical alloying and subsequent heat treatment. Nanometer-sized grains were observed in the as-milled crystalline powders in all compositions. Crystallite sizes were calculated using the Scherrer formula and found to be in the order of 10-20 nm after 360 minutes of milling time for all compositions. The XRD data show considerable solid solubility extension in these powders, and formation of intermetallic phases due to mechanical alloying and subsequent annealing. These changes are discussed in the context of the Al-Cu phase diagram.     

1.5 mu m compressive-strained multiquantum-well 20-wavelength distributed-feedback laser arrays

The wide gain spectrum of compressive-strained multiquantum-well active layers was used to fabricate 20-wavelength distributed-feedback laser arrays. A record wide-wavelength span of 131 nm in the 1.5 mu m wavelength region was demonstrated. The maximum intrinsic modulation response, measured by a parasitic-free optical modulation technique, reaches 16 GHz.<>     

DEVELOPMENTS AND CHALLENGES IN FLAVOR PERCEPTION AND MEASUREMENT—A REVIEW

Flavor perception and measurement play important roles in the development of food products. In an increasingly commercial environment, the food industry must strive to minimize adverse consumer reactions. This article gives an extensive overview on the various methods used for flavor measurement. Principles of flavor release and perception are discussed and applications to quality assessment are demonstrated.     

Composition and temperature dependence of the direct band gap of GaAs1−xNx (0≤x≤0.0232) using contactless electroreflectance

The composition and temperature dependence (20K<T<380K) of the direct gap, E₀, of a series of GaAs_1−xN_x/GaAs (0≤x≤0.0232) samples has been measured using contactless electroreflectance. Our results for the composition dependence of E₀ are different in relation to a recent experiment [W.G. Bi and C.W Tu, Appl. Phys. Lett. 70, 1608 (1997)]. In contrast to previously reported results, we find that the temperature dependence of the direct gap is in fact dependent on N composition and that the parameters which describe the temperature dependence of the band gap lie between those of GaAs and GaN.